Mechanical properties of reinforced concrete beams with axial tension and initial cracks due to thermal stress, concrete shrinkage, etc. were investigated. Flexural loading tests were carried out using 27 beam specimens, which were reinforced with various amount of steel bars. Axial tension and initial cracks of each specimen were also varied as parameters. 　As the results of the tests, intial flexural rigidity decreased, and deflection and crack width increased due to axial tension and initial crackcs. The crack width increased in proportion to strain of renforcement. Flexural yield moment decreased when axial tension was applied, and existing calculation method could predict the decrease of the yield moment. The existence of the initial cracks did not affect the yield moment. Strain of shear reinforcement chould be calculated by truss theory,. Axial tension and initial cracks did not have much effect on the properties of shear cracks and shear capacity.